A chassis includes an internal portion which corresponds to a rifle action of a first type. The chassis further includes an external portion which corresponds with a rifle stock. The chassis is attached to the rifle action of the first type and to rifle stock.

A modular bolt action rifle is provided, having an upper receiver configured to receive a bolt action bolt housing and bolt and a first universal fitting at a front of the upper receiver configured to receive one of a plurality of commonly sourced rifle barrels, and a lower receiver integral to or coupled to the upper receiver. The lower receiver is configured to receive commonly sourced fire control group components and a commonly sourced bolt action trigger mechanism. The lower receiver includes a second universal fitting at a rear of the lower receiver configured to receive one of a plurality of commonly sourced butt stocks.

A apparatus implementable on a firearm includes a handguard assembly which is configured to at least partially surround a barrel of the firearm when the handguard is installed on the firearm. The handguard includes at least first and second physical features such that: (a) the first physical feature is configured to accommodate mounting of an accessory of the firearm on the handguard, and (b) the second physical feature is configured to secure a cable of the accessory onto the handguard.

A firearm includes a barrel having a breech end. An upper receiver is engaged with the breech end of the barrel such that a majority of the barrel is outside of the upper receiver. A lower receiver is releasably connected to the upper receiver, and the firearm includes structure for slidingly connecting the upper receiver to the lower receiver.

A firearm includes a barrel having a breech end. An upper receiver is engaged with the breech end of the barrel such that a majority of the barrel is outside of the upper receiver. A lower receiver is releasably connected to the upper receiver, and the firearm includes structure for slidingly connecting the upper receiver to the lower receiver.

An unfinished firearm frame having a top adapted to receive a slide. Where rear restriction protrusions extend from the top of the frame near a rear of the frame which restricts addition of the slide to the frame and front restriction protrusions extend from the top of the frame and forward of the at least one rear restriction protrusion which restricts addition of the slide to the frame. Where there is a recoil assembly block adapted to prevent a recoil assembly from being assembled into the frame. A jig having a right side and a left side to receive and clamp the frame. The jig including three pin hole guides, a removal guide edge for each of the at least one rear restriction protrusion and the at least one front restriction protrusion and a recoil assembly cutout to allow a tool to pass to the recoil assembly block.

An unfinished firearm frame having a top adapted to receive a slide. Where rear restriction protrusions extend from the top of the frame near a rear of the frame which restricts addition of the slide to the frame and front restriction protrusions extend from the top of the frame and forward of the at least one rear restriction protrusion which restricts addition of the slide to the frame. Where there is a recoil assembly block adapted to prevent a recoil assembly from being assembled into the frame. A jig having a right side and a left side to receive and clamp the frame. The jig including three pin hole guides, a removal guide edge for each of the at least one rear restriction protrusion and the at least one front restriction protrusion and a recoil assembly cutout to allow a tool to pass to the recoil assembly block.

A modular system for a firearm receiver which has a threaded annulus at a rear end thereof. The modular system includes a base that includes a front face, a rear face, and a thread helically extending along an exterior thereof between the front face and rear face and configured to engage with the threaded annulus of the receiver. The base includes a screw opening extending through the front and rear faces. The system also includes a screw and a first end cap. The first end cap has a body. The body has a front face and a threaded opening extending into the body and terminating therein. The screw has a threaded shank configured to extend through the screw opening of the base and into the threaded opening of the first end cap for connecting the base and first end cap.

An upper receiver assembly of a firearm is disclosed. The upper receiver assembly contains a barrel, an extension block removably coupled with the barrel, an upper receiver removably coupled with the extension block, a handguard mounting block removably coupled with the barrel, and a handguard removably coupled with the handguard mounting block.

An upper receiver assembly of a firearm is disclosed. The upper receiver assembly contains a barrel, an extension block removably coupled with the barrel, an upper receiver removably coupled with the extension block, a handguard mounting block removably coupled with the barrel, and a handguard removably coupled with the handguard mounting block.